Cellulose fiber

ABSTRACT

The present invention relates to a fiber of the Lyocell type which has a titer of from 0.8 dtex to 3.3 dtex and is characterized by the following relationships:
         Höller factor F2≥1, preferably ≥2   Höller factor F1≥−0.6   Höller factor F2≤6 and   Höller factor F2 minus 4.5*Höller factor F1≥1, preferably ≥3.       

     The fiber according to the invention displays a specific combination of properties with regard to the Höller factors, the flexibility and the abrasion resistance within a planar assembly. Hence, the fiber shows a behavior more similar to viscose and can be processed in the textile chain according to viscose standard methods.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a cellulosic fiber of the Lyocell type.

In consequence of the environmental problems associated with the knownviscose process for the production of cellulosic fibers, intense effortshave been made in recent decades to provide alternative and moreenvironmentally friendly methods. A particularly interesting possibilitywhich thereby has arisen in recent years is to dissolve cellulose in anorganic solvent without a derivative being formed and to extrude mouldedbodies from said solution. Fibers spun from such solutions have receivedthe generic name Lyocell from BISFA (The International Bureau for theStandardization of man-made fibers), wherein an organic solvent isunderstood to be a mixture of an organic chemical and water.

Furthermore, such fibers are also known by the term “solvent-spunfibers”.

It has turned out that in particular a mixture of a tertiary amine oxideand water is perfectly suitable as an organic solvent for the productionof Lyocell fibers and other moulded bodies, respectively. Thereby,N-methylmorpholine-N-oxide (NMMO) is predominantly used as the amineoxide. Other suitable amine oxides are disclosed in EP-A 553 070.

In EP 0 356 419 A, a technical implementation of the method of producinga solution of a pulp in an amine oxide is described. In doing so, asuspension of the crushed pulp is conveyed in an aqueous tertiary amineoxide in the form of a thin layer across a heating surface, water isevaporated and, thereby, a spinnable cellulose solution is produced.

A method of spinning cellulose solutions in amine oxides is known fromU.S. Pat. No. 4,246,221. According to said method, filaments extrudedfrom a spinneret are guided through an air gap, drawn therein and,subsequently, the cellulose is precipitated in an aqueous spinning bath.The method is known as a “dry/wet spinning process” or also as an“air-gap spinning process”.

The entire method of producing fibers from solutions of cellulose in atertiary amine oxide is referred to in the following as an “amine oxideprocess”, with the abbreviation “NMMO” denoting hereinafter all tertiaryamine oxides which are able to dissolve cellulose. Fibers producedaccording to the amine oxide process are characterized by a high fiberstrength in the conditioned state as well as in the wet state, a highwet modulus and a high loop strength.

The conditions within the air gap such as temperature, humidity, coolingrate of the filaments as well as draft dynamics are of greatsignificance for the properties of the resulting fibers (see, in thisconnection, the publication by Volker Simon in “Transactions of theAmerican Society of Mechanical Engineers (ASME) 118 (1996) No. February,p. 246-249”).

Technical embodiments of the spinning process have been described innumerous documents:

WO 93/19230 describes a method wherein the extruded filaments are cooledjust beneath the nozzle by being blasted with air. WO 94/28218 describesa nozzle design and a blowing method. WO 95/01470 claims a laminar flowof the cooling gas stream described in WO 93/19230. WO 95/04173describes a further technical implementation of blowing. In WO 96/17118,the moisture content of the blowing air is defined. In WO 01/68958, theblowing air stream is directed downwards toward the extruded filamentsat an angle of from 0° to 45°. WO 03/014436 describes a blowing devicecomprising a suction of the blowing air. WO 03/057951 claims theshielding of part of the air gap from the blowing air. In WO 03/057952,a turbulent gas stream for cooling the filaments is described. WO05/116309 likewise describes the shielding of part of the air gap fromthe blowing air.

The fibers/filaments obtained according to the air-gap spinning processdiffer in structural terms from known viscose fibers. While thecrystalline orientation is approximately at the same high level both inviscose fibers and in Lyocell fibers (a largely parallel arrangement ofthe cellulose chains located in the structured areas of the fiberrelative to the fiber axis), considerable differences exist in theamorphous orientation (a higher parallelism of the random portions inLyocell fibers).

The particularities of the Lyocell fiber such as a high crystallinity,long and thin crystallites and a high amorphous orientation prevent anadequate bond of the crystallites transversely to the fiber axis. In thewet state, the swelling of the fibers additionally reduces the bondingforces transversely to the fiber axis and thus leads to the separationof fiber fragments under mechanical strain. This behavior is referred toas wet fibrillation and causes quality losses in the form of greying andhairiness in the final textile product.

Surveys of the state of research in this field are provided by the worksof Josef Schurz, Jürgen Lenz: “Investigations on the structure ofregenerated cellulose fibers” in Macromolecular Symposia, Volume 83,Issue 1, pages 273-289, May 1994, and Fink H-P, Weigel P, Purz H-J,Ganster J “Structure formation of regenerated cellulose materials fromNMMO-solutions” Prog. Polym. Sci. 2001 (26) p. 1473-1524.

Previous efforts to improve the wet-fibrillation resistance of Lyocellfibers were aimed in two directions:

varying the manufacturing conditions, or

introducing a step of chemical cross-linking during the productionprocess

However, it is hardly possible to evaluate the success of the measuresof reducing fibrillation which have been described in each case. Thereis no standardized method of measuring the fibrillation behavior, andall the methods applied in the patent literature are proprietary.

The second procedure, chemical cross-linking, is associated with anumber of drawbacks such as

additional chemicals/costs of chemicals/waste water problems during theproduction of the fiber

environmental pollution during the production of the cross-linkingchemicals

inadequate hydrolysis stability of cross-linking under the conditions oftextile processing.

Examples of the procedure of chemical cross-linking are described in EP0 53 977 A, EP 0 665 904 A and EP 0 943 027 A, respectively.

Numerous documents have been published with regard to the firstprocedure, varying the manufacturing conditions. However, the describedmethods have either brought about only a slight improvement in thefibrillation behavior, which has not been reflected in a lastingimprovement of processability, or the methods have failed to be feasibleon a large scale as a result of the costs/technical expenditures.

In SU 1,224,362, a dope is spun from a single pulp into a bathcontaining NMMO in amyl alcohol or isopropanol, respectively. WO92/14871 claims a fiber with a reduced fibrillation, characterized inthat the pH of the spinning bath and of subsequent washing baths isbelow 8.5. No details are given about the type of the pulp or thespinning conditions.

WO 94/19405 describes a method wherein a pulp mixture is used. However,no reference is made to the tendency toward fibrillation of the fiberswhich have been spun.

WO 95/02082 describes a combination of process parameters, illustratedin a mathematical expression, for the production of a fiber with a lowtendency toward fibrillation. Said process parameters are the diameterof the spinning hole, the output of spinning mass, the titer of thefilaments, the width of the air gap and the humidity in the air gap. Thepulp used is not described in detail, the spinning temperature is only115° C.

In WO 95/16063, the extruded filaments are contacted in the spinningbath or in the aftertreatment baths, respectively, with a surfactant ina dissolved form. The type of the pulp used is not specified, thespinning temperature is 115° C.

WO 96/07779 uses an organic solvent, preferably polyethylene glycol, asa spinning bath. No details are given about the pulp used or thetextile-mechanical properties of the obtained fibers. 110° C. isindicated as the spinning temperature.

In WO 96/07777, the extruded filaments are contacted in the air gap withan aliphatic alcohol provided in a gaseous form. The type of the pulpused is not specified, the spinning temperature is 115° C.

WO 96/20301 describes a method wherein the moulded solution is guidedconsecutively through at least two precipitation media, with a slowercoagulation of the cellulose occurring in the first precipitation mediumas compared to the latter precipitation medium. In the examples, ahigher alcohol is preferably used as the first precipitation medium. Thepulp used is not indicated, the spinning temperature amounts to 115° C.

WO 96/21758 describes a method wherein the moulded solution is blastedin the air gap in an upper zone with air having a higher moisturecontent and in a lower zone with air having a lower moisture content.Single pulps of various degrees of polymerization are used as pulps, thespinning temperature amounts to 115° C.

EP 0 853 146 describes a two-stage method wherein the dwell time of thefibers in the first precipitation stage is adjusted such that merely thestickiness of the surface of the solution moulded into fibers isprevented and the fibers are coagulated without tension in a laterprecipitation stage. In the examples, the spinning temperature amountsto 109-112° C.

In WO 97/23669, spinning takes place into a spinning bath having acontent of NMMO of more than 60%. A single pulp is used.

In WO 97/35054, a combination of parameters for obtaining a fiber low infibrillation is described, namely the concentration of the dope, thedraft in the air gap as well as the diameter of the nozzle hole. Asingle pulp is used, the spinning temperature ranges from 80 to 120° C.

In WO 97/38153, a combination of parameters for obtaining a fiber low infibrillation is likewise described, namely the length of the air gap,the spinning rate, the dwell time in the air gap, the speed of theblowing air in the air gap, the moisture content of the blowing air aswell as the product of the dwell time in the air gap times the moisturecontent of the blowing air. A single pulp is used as the pulp.

In WO 97/36028, the fibers are treated with a solution of 40-80% NMMO,optionally with an additive being added, upon leaving the precipitationbath.

In WO 97/36029, the fibers are treated with a solution of zinc chlorideupon leaving the precipitation bath.

In WO 97/46745, the fibers are treated with a solution of NaOH uponleaving the precipitation bath.

In WO 98/02602, the fibers are treated with a solution of NaOH uponleaving the precipitation bath in a relaxed state.

In WO 98/06745, a pulp mixture is used which is obtained by mixingsolutions of pulps of different degrees of polymerization. No detailsare given with regard to the spinning temperature.

In WO 98/09009, the addition of additives (polyalkylenes, polyethyleneglycols, polyacrylates) to the spinning mass is described. A single pulpis used as the pulp.

In WO 98/22642, a pulp mixture having a low degree of polymerization isused. The spinning temperature amounts to 110-120° C.

Also in WO 98/30740, a pulp mixture is used, the spinning mass is spunaccording to a centrifugal spinning process. The spinning temperatureamounts to 80-120° C.

In WO 98/58103, details about the molecular weight distribution of thepulp in a spinning mass from a pulp mixture are indicated, which lead tostable spinning. However, no reference is made to the fibrillationbehavior of the obtained fibers/filaments.

In DE 19753190, the fibers are treated with a concentrated NMMO solutionupon leaving the precipitation bath.

In GB 2337990, a co-solvent is used for dissolving the single pulp. Thenascent solution is spun at 60-70° C.

In U.S. Pat. No. 6,471,727, a spinning mass from a single pulp with ahigh content of hemicellulose and lignin is processed according to adry/wet or meltblown spinning process, respectively.

In WO 01/81663, a spinneret is described in which the spinning capillaryis directly heated close to the outlet cross-section. Said measure issupposed to reduce the tendency toward fibrillation of Lyocell fibers,however, no test conditions are specified for this.

WO 01/90451 describes a spinning method characterized by a mathematicalrelationship including the heat flux density in the air gap and theratio of length to diameter of the extrusion channel. Fibers spunaccording to the invention are proposed to display a lower tendencytoward fibrillation, however, no further details are given in thisconnection.

In U.S. Pat. No. 6,773,648, a meltblown process for the production of afibrillation-reduced fiber is made public. Due to their irregulartiters, meltblown fibers are unsuitable for textile use.

In DE 10203093, a fiber with a low fibrillation is produced by spinningtwo dopes of different cellulose concentrations from a single pulp froma biocomponent nozzle. No example is given.

In DE 10304655, polyvinyl alcohol is added to the NMMO in order toimprove the quality of the solution. The conditions for spinning theclaimed less fibrillating fiber are not indicated.

The specific structure of the Lyocell fiber leads, on the one hand, toexcellent textile-mechanical properties such as a high strength in boththe dry and wet states as well as to a very good dimensional stabilityof the planar assemblies produced therefrom and, on the other hand, tolittle flexibility (high brittleness) of the fibers, which manifestsitself in a decrease in the abrasion resistance in comparison to viscosefibers within the planar assembly.

The term flexibility (compliance) is defined, according to Hooke's Law,as the quotient from the elongation of the test body and the loadcausing the elongation. Increasing the flexibility of Lyocell fibers isthe object of a number of publications:

A flexible Lyocell fiber is described in EP 0 686 712. The patent claimsa fiber with a reduced NMR degree of order, obtained by addingnitrogenous substances such as urea, caprolactam or aminopropanol to thepolymer solution or into the precipitation bath, respectively. However,a fiber with a very low wet strength is obtained; thus, the fiberdiffers distinctly from the fibers according to the invention asdescribed below.

In WO 97/25462, a method for the production of a flexible andfibrillation-reduced fiber is described, wherein, after theprecipitation bath, the moulded fiber is guided through a washing andaftertreatment bath containing an aliphatic alcohol, in addition,optionally, with an additive of sodium hydroxide. The properties of theobtained fibers are described only very insufficiently. In particulardata about the dry and wet strengths are missing, which would allowclassification in the “Höller chart”, as described in further detailbelow.

It may be said, however, that, in the examples of the presentapplication, the fiber shows considerable differences in a comparison ofthe fiber elongations indicated in said document with the correspondingdata of the fibers according to the invention and that, due to the lowvalues of elongation as indicated in said document, the flexibility ofthe fiber cannot be very high according to the above-mentioneddefinition of flexibility. The improvement in the fibrillation behavioras mentioned in the text of the document is not confirmed by any datawhatsoever.

Documents EP 1 433 881, EP 1 493 753, EP 1 493 850, EP 1 841 905, EP 2097 563 and EP 2 292 815 describe fibers and filaments, respectively,preferably for the application tyre cord, produced by adding polyvinylalcohol to the NMMO/dope. The fibers/filaments are characterized by highstrength, but little elongation. Accordingly, their flexibility can onlybe minor according to the above-mentioned definition.

Further publications which indicate that, by adding additives to thespinning mass, influence can be exerted on the fibrillation behaviorand/or the flexibility of the fiber, are

-   Chanzy H, Paillet m, Hagege R “Spinning of cellulose from    N-methylmorpholine N-oxide in the presence of additives” Polymer    1990, 31, p 400-5-   Weigel P, Gensrich J, Fink H-P “Strukturbildung Cellulosefasem aus    Aminoxidlösungen” Lenzinger Berichte 1994; 74(9), p 31-6 and-   Mortimer S A, Peguy A A “Methods for reducing the tendency of    lyocell fibers to fibrillate” J. appl. Polym. Sci. 1996, 60, p    305-16.

WO 2014/029748 (not pre-published) discloses the manufacture ofsolvent-spun cellulosic fibers, especially from solutions in ionicliquids. Further state of the art in this regard is known from DE 102011 119 840 A1, AT 506 268 A1, U.S. Pat. No. 6,153,136, CN 102477591A,WO 2006/000197, EP 1 657 258 A1, US 2010/0256352 A1, WO 2011/048608 A2,JP 2004/159231 A and CN 101285213 A.

The invention of viscose fibers (Cross and Bevan 1892, GB 8700) occurredmore than a hundred years ago. Despite weaknesses in the production(environmental problems) and the properties (poor washing behavior ofthe standard type), more than one million tons of said fiber type isproduced each year.

The further development of the old process after the second world war(polynosic and modal fibers) resulted in fibers with a better washingbehavior and a higher dimensional stability, but was unable to changethe intrinsic properties of the method (environmental relevance as wellas, due to the large number of process steps, an extremely complicatedmethod).

Conversely, it became apparent during the development of the new fibertype “Lyocell” that, due to its varying structure, the fiber placesspecial demands on the processing conditions and, thus, the establishedmethods of processing a viscose or modal fiber cannot be applied in thetextile chain. Special machines and processing adjustments which areadapted to the fiber are required especially for dyeing and wetfinishing. Today, more than 20 years after the Lyocell fiber was placedon the market, this is still regarded as a disadvantage.

Now it would be desirable to impart particular properties of the viscosefiber such as

a lower tendency toward fibrillation in the wet state

higher flexibility (less brittleness)

to the Lyocell fiber while maintaining the excellent properties of theLyocell fiber (such as, e.g., a high wet strength, a high wet modulusand, hence, a washability and a dimensional stability which, incomparison to viscose fibers, are substantially improved).

It is thus an object of the present invention to provide a Lyocell fiberwith properties more similar to viscose by means of which processing ofthe fiber according to the well-known and established methods of viscoseprocessing is rendered possible.

The change in properties should be achieved solely by choosing suitableprocess parameters for the production of the fiber, without having tofall back on chemicals extraneous to the process as additives to eitherthe spinning mass, the spinning bath or during the aftertreatment. Everyadditional chemical in the system, be it as an additive to the spinningmass or to the spinning bath, necessitates increased efforts for therecovery and constitutes a cost factor.

The object of the present invention is achieved by a cellulosic fiber ofthe Lyocell type which has a titer of from 0.8 dtex to 3.3 dtex and ischaracterized by the following relationships:

Höller factor F2≥1, preferably ≥2

Höller factor F1≥−0.6

Höller factor F2≤6 and

Höller factor F2 minus 4.5*Höller factor F1≥1, preferably ≥3.

SHORT DESCRIPTION OF THE FIGURES

FIG. 1 shows a Höller chart of commercially available fibers fromregenerated cellulose prior to the development of the Lyocell fiber.

FIG. 2 shows the area in the Höller chart in which the fibers accordingto the invention are located.

FIG. 3 shows a Höller chart in which the fiber according to theinvention is contrasted to a common Lyocell fiber.

DETAILED DESCRIPTION OF THE INVENTION

In the following, the new Lyocell fibers according to the invention aredescribed by reference to the so-called “Höller factors” F1 and F2 andare distinguished from known cellulosic man-made fibers of the priorart.

While the basic chemical structure of man-made cellulosic fibers suchas, e.g., viscose fibers, but also of Lyocell fibers, is essentially thesame (cellulose), the fibers differ in factors such as, e.g., thecrystallinity or also the orientation in particular of amorphous areas.It is difficult to quantitatively distinguish those factors from eachother.

It is also apparent to a person skilled in the art that a Lyocell fiberdiffers, for example, from a viscose fiber in textile-mechanicalparameters (such as, e.g., strength values), but also in propertieswhich can be defined less clearly, e.g., the textile “grip”. Likewise,there are considerable differences between the different types ofcellulose fibers produced according to the viscose process such as,e.g., a (standard) viscose fiber, a modal fiber or a polynosic fiber.

In the essay by R. Höller “Neue Methode zur Charakterisierung von Fasemaus Regeneratcellulose” Melliand Textilberichte 1984 (65) p. 573-4, aclear differentiation between the different fiber types made ofregenerated cellulose known at the time, i.e., the fibers producedaccording to the viscose process, could be presented on the basis ofquantitative features.

According to this suggestion the complexity of the comparison of agreater number of fiber properties could be simplified significantly byway of formation of few parameters splitting fibers into groups ofsimilar properties and by factor analysis. Factor analysis is amultivariate statistical method which makes it possible to reduce agroup of correlated features to a smaller number of uncorrelatedfactors.

The textile-mechanical properties used by Höller for factor analysiswere the maximum tensile force conditioned (FFk) and wet (FFn), themaximum tensile force elongation conditioned (FDk) and wet (FDn), thewet modulus (NM), the loop strength conditioned (SFk) as well as theknot strength conditioned (KFk).

All those measurands as well as their determination are known to aperson skilled in the art, see, in particular, BISFA regulation “Testingmethods viscose, modal, lyocell and acetate staple fibers and tows”Edition 2004 Chapters 6 and 7, and will be described in further detailbelow.

In the fiber collective available to Höller, 87% to 92% of the variancebetween the samples could be detected by merely two factors (see FIG.1). Those two factors are calculated as follows:

Höller factorF1=−1.109+0.03992×FFk−0.06502×FDk+0.04634×FFn−0.04048×FDn+0.08936×NM+0.02748×SFk+0.02559×KFk

Höller factorF2=−7.070+0.02771×FFk+0.04335×FDk+0.02541FFn+0.03885FDn−0.01542×NM+0.2891×SFk+0.1640×KFk.

As can be seen in FIG. 1, a clear differentiation between the differentfiber types could be illustrated by way of this analysis—drawn up on thebasis of clearly measurable parameters.

FIG. 1 shows in the coordinate system of Höller factors F1 and F2 thefiber collective made up of 70 samples of commercially available fibersof regenerated cellulose which has been examined by Höller. Along factorF1, it is possible to identify the division into (standard) viscosefibers and modal fibers, which are also listed by BISFA as differentfiber types (although they are produced according to the same basicmethod, namely the viscose process). To the left of the ordinate, theregion of (standard) viscose fibers is shown (designated as “V” in FIG.1). Essentially to the right of the ordinate the region of modal fibersis shown, which are further structured in two sub-groups, i.e. fibers ofthe HWM-type (“HWM”—high wet modulus) and fibers of the polynosic type(“PN”). In addition, a (dashed) boundary is plotted in the graph, beyondwhich none of the fibers made of regenerated cellulose and examined atthe time were located. However, at the time of this publication, Lyocellfibers were still in the trial stage and not commercially available.

Lyocell fibers which currently are commercially available have Höller F1values of 2 to 3 and F2 values of 2 to 8. In the “Höller chart”according to FIG. 1, such fibers would therefore be located beyond theabove-mentioned boundary, from which the considerable difference betweenthe fibers of the viscose group and the Lyocell fibers is apparentalready purely visually.

The fiber according to the invention is now located in an area of theHöller chart which can be illustrated by a square.

The sides of the square correspond to the following values orrelationships, respectively:

Lower boundary F2=1

Left-hand boundary F1=−0.6

Upper boundary F2=6

Right-hand boundary defined via the relationship:

Höller factor F2 minus 4.5*Höller factor F1≥1, preferably ≥3

The arrangement of the Lyocell fiber according to the invention in theHöller chart resulting from said relation is shown in FIG. 2. Looselyspeaking, the fiber according to the invention thus occupies in theHöller chart the space above the abscissa and around the ordinate aswell as to the left thereof and is clearly distinguished from Lyocellfibers which are currently commercially available and, in the Höllerchart, are located, loosely speaking, (considerably) to the right of theordinate.

Conversely, the Lyocell fiber according to the invention is located inthe Höller chart close to the area of the (standard) viscose. Actually,it has been shown that the Lyocell fiber according to the invention has,with regard to its processability, properties which are by far “moresimilar to viscose” than those of Lyocell fibers which are currentlycommercially common.

In textile practice, these “more viscose-like” properties lead to thefollowing property changes:

The fiber according to the invention can be dyed as a planar assemblylike viscose in a strand (conventional Lyocell fibers are only suitablefor open-width dyeing).

Planar assemblies (such as knitted fabrics) made of the fiber accordingto the invention, which have not been subjected to high-grade finishingwith a resin finish, will keep an unchanged fabric appearance for alonger time when being washed.

Planar assemblies made of the fiber according to the invention exhibitan abrasion resistance similar to planar assemblies made of viscose andhence display an improvement by the double in comparison to conventionalLyocell fibers.

However, the fiber according to the invention retains during washingprocesses the high dimensional stability which is characteristic of theLyocell fiber.

Although the areas of the fiber according to the invention and of(standard) viscose fibers as well as, partially, of modal fibers overlapin the Höller chart, the fiber types can, however, clearly bedifferentiated from each other based on basic differences in themanufacturing process, since the fiber according to the invention can beanalytically distinguished unambiguously from fibers produced accordingto the viscose process such as (standard) viscose fibers and modalfibers:

A residual amount of solvent associated to the fiber type Lyocell isdetectable (in particular residues of NMMO in case of fibers producedaccording to the amine oxide process).

Unlike a fiber produced according to the viscose process, the fibercontains no sulphur.

According to the method described below, the wet abrasion behavior ofthe fiber according to the invention ranges between 300 and 5000revolutions up to the point of fiber breakage, preferably between 500and 3000 revolutions.

The flexibility (i.e., the quotient FDk/FFk) of the fiber according tothe invention preferably ranges between 0.55 and 1.00, preferablybetween 0.65 and 1.00.

It has been shown that the dry abrasion according to Martindale of asingle jersey 150 g/m² made of a ring yarn Nm 50/1 of the fiberaccording to the invention may range between 30 000 and 60 000 tours upto the point of hole formation.

The fiber according to the invention is preferably characterized in thatit is produced according to the amine oxide process.

The fiber according to the invention is preferably provided as a staplefiber, i.e., as cut fibers.

The property change according to the invention of Lyocell fibers towarda Lyocell fiber similar to viscose and hence the repositioning of thefiber data in the Höller chart is achieved, according to the presentinvention, by carefully adjusting the raw material and the processconditions:

1) Pulp

A defined molecular weight distribution of the raw material used isrequired for the production of the fiber according to the invention.This is achieved in particular by mixing two or more single pulps.Accordingly, the fiber according to the invention is preferablycharacterized in that it is produced from a mixture of at least twodifferent pulps.

The molecular weight distribution is characterized by the followingparameters:

a) The amount of celluloses or accompanying substances of cellulose(polymeric pentosans and hexosans such as xylan, glucomannan,low-molecular beta-1,4-glucan) with a degree of polymerization of lessthan 50 is below 2% (based on the pulp mixture), preferably below 1.5%(determination of the molecular weight distribution with GPC/SEC byMALLS detection in DMAC/LiCl, Bohm, R., A. Potthast, et al. (2004). “Anovel diazo reagent for fluorescence labeling of carboxyl groups inpulp.” Lenzinger Berichte 83: 84-91).

b) An amount of 70% to 95% of the pulp mixture has a limiting viscositynumber ranging from 250 to 500 ml/g, preferably from 390 to 420 ml/g(measured according to SCAN-CM 15:99), in the following referred to asthe “low-molecular component”.

c) An amount of 5% to 30% of the pulp mixture has a limiting viscositynumber of from 1000 to 2500 ml/g, preferably of 1500-2100 ml/g, in thefollowing referred to as the “high-molecular component”.

d) Preferably, the amount of the low-molecular component is 70-75%, ifthe high-molecular component has a limiting viscosity number of1000-1800 ml/g, and, respectively, 70-95%, if the high-molecularcomponent has a limiting viscosity number of >2000 ml/g.

e) Furthermore, the purity of the pulps used is important: The purity isdefined as the mean value of alkali resistances R10 and R18 according toDIN 54355 (1977), i.e. the determination of the resistance of pulpagainst caustic soda (alkali resistance). Said value approximatelycorresponds to the content of alpha cellulose according to TAPPI T 203CM-99.

The purity of the low-molecular component is >91%, preferably >94%, thepurity of the high-molecular component is >91%, preferably >96%.

It has been shown that, in particular by using high-purity pulps such ascotton linter pulps, it is possible more easily to produce fibersdisplaying the properties according to the invention.

Furthermore, it has been shown that pulps made from reclaimed cottontextiles (“reclaimed cotton fibers”—RCF) are suitable for themanufacture of the fibers according to the invention. Such pulps can beproduced according to the teaching of the publication “Process forpretreating reclaimed cotton fibers to be used in the production ofmoulded bodies from regenerated cellulose” (Research Disclosure,www.researchdisclosure.com, database number 609040, published digitallyDec. 11, 2014).

2) Spinning Conditions

In addition to choosing the appropriate pulp composition, the spinningconditions for producing the fiber according to the invention are ofparticular importance:

i) The throughput of spinning mass should range between 0.01 and 0.05g/nozzle hole/min, preferably between 0.015 and 0.025 g/nozzle hole/min.

ii) Air gap length: The procedure of producing the fiber according tothe invention differs from the prior art (WO 95/02082, WO 97/38153) inthat the air gap length does not constitute a relevant parameter. Fibersaccording to the invention are obtained already with an air gap lengthstarting from 20 mm.

iii) Climate within the air gap: The production of the fiber accordingto the invention also differs from the prior art (WO 95/02082, WO97/38153) in that the humidity and the temperature of the blowing air donot constitute relevant parameters. Humidity values of the blowing airof between 0 g/kg air and 30 g/kg air are applicable, and thetemperature of the blowing air may range between 10° C. and 30° C. (itis known to a person skilled in the art that, for a given humiditysetpoint of the blowing air, a minimum air temperature corresponding toa relative humidity of 100% cannot be fallen short of).

The speed of the blowing air in the air gap is lower than for theproduction of Lyocell fibers which currently are commercially availableand should be below 3 m/sec, preferably at about 1-2 m/sec.

iv) Draft in the air gap: The value of the draft in the air gap(quotient of the haul-off speed from the spinning bath to the extrusionspeed from the nozzle) should be below 7. Given a defined titer of thefiber, a small draft is achievable by using nozzles with small holediameters. Nozzles having a hole diameter of ≤100 μm are usable, nozzleshaving a hole diameter of between 40 μm and 60 μm are preferred.

v) Spinning temperature: Spinning must occur at a temperature as high aspossible, which is limited only by the thermostability of the solvent.However, it must not fall short of a value of 130° C.

vi) The spinning bath temperature may range between 0° C. and 40° C.,values of from 0° C. to 10° C. are preferred.

vii) During the transport of the fiber from the spinning bath into theaftertreatment and during the aftertreatment, the filaments should beexposed, according to WO 97/33020, to a tensile load in the longitudinaldirection of not more than 5.5 cN/tex.

It has been shown that, if the above parameters are met, Lyocell fiberswhich comply with the relations according to the invention with regardto the two Höller factors F1 and F2 and thus have more “viscose-like”properties are obtained in a reproducible way.

The present invention also relates to a fiber bundle comprising aplurality of fibers according to the invention. A “fiber bundle” isunderstood to be a plurality of fibers, for example, a plurality ofstaple fibers, a strand of continuous filaments or a bale of fibers.

Measuring Methods: Testing of Textile-Mechanical Properties:

The determination of the titer of the fibers (linear density) wascarried out according to BISFA regulation “Testing methods viscose,modal, lyocell and acetate staple fibers and tows” Edition 2004 Chapter6 by means of a vibroscope, type Lenzing Technik.

The determination of the maximum tensile force (breaking tenacity), ofthe maximum tensile force elongation (elongation at break) in theconditioned and wet state, and of the wet modulus was carried out,according to the above-mentioned BISFA regulation, Chapter 7, by meansof a tensile testing device Lenzing Vibrodyn (device for tensile testson single fibers at a constant deformation speed).

The loop strength was determined on the basis of DIN 53843, Part 2, inthe following way:

The titers of the two fibers used for the test are determined on thevibroscope. For determining the loop strength, the first fiber is formedinto a loop and clamped with both ends into the pre-load weight (size ofthe pre-load weight according to the above-mentioned BISFA regulation,Chapter 7). The second fiber is drawn into the loop of the first fiberand the ends are placed into the upper clamp (measuring head) of thetensile testing device in such a way that the interlacing is located inthe middle of the two clamps. After the pre-load has levelled out, thelower clamp is closed and the tensile test is started (clamping length20 mm, traction speed 2 mm/min). It should be made sure that thebreakage of the fiber occurs at the loop arc. As a titer-related loopstrength, the measured maximum tensile force value, which has beenobtained, is divided by the smaller one of the two fiber titers.

The knot strength was determined on the basis of DIN 53842, Part 1, inthe following way:

A loop is formed from the fiber to be tested, one end of the fiber isdrawn through the loop and, thus, a loose knot is formed. The fiber isplaced into the upper clamp of the tensile testing device in such a waythat the knot is located in the middle between the clamps. After thepre-load has levelled out, the lower clamp is closed and the tensiletest is started (clamping length 20 mm, traction speed 2 mm/min). Forthe evaluation, only results are used in which the fiber has actuallybroken at the knot.

Determination of the Fibrillation Behavior According to the Wet AbrasionMethod:

The method described in the publication by Helfried Stöver: “ZurFasernassscheuerung von Viskosefasern” Faserforschung und Textiltechnik19 (1968) Issue 10, p. 447-452, was employed.

The principle is based on the abrasion of single fibers in the wet stateusing a rotating steel shaft coated with a viscose filament hose. Thehose is continuously moistened with water. The number of revolutionsuntil the fiber has been worn through and the pre-load weight triggers acontact is determined and related to the respective fiber titer.

Device: Abrasion Machine Delta 100 of Lenzing Technik InstrumentsDeparting from the above-cited publication, the steel shaft iscontinuously shifted in the longitudinal direction during themeasurement in order to prevent the formation of grooves in the filamenthose.

Source of supply of the filament hose: Vom Baur GmbH & KG. Marktstraße34,

D-42369 Wuppertal Test Conditions:

Water flow rate: 8.2 ml/minSpeed of rotation: 500 U/minAbrasion angle: 40 for titer 1.3 dtex, 500 for titer 1.7 dtex, 500 fortiter 3.3 dtex Pre-load weight: 50 mg for titer 1.3 dtex, 70 mg fortiter 1.7 dtex, 150 mg for titer 3.3 dtex

Determination of the Abrasion Resistance of Planar Assemblies Accordingto Martindale:

Methods according to the standard “Determination of the AbrasionResistance of Planar Textile Assemblies by means of the MartindaleMethod—Part 2: Definition of the Destruction of Samples (ISO12947-2:1998+Cor.1:2002; German version EN ISO 12947-2:1998+AC:2006).

Examples

The pulps and pulp mixtures, respectively, described below in Table 1were processed into spinning masses of the composition indicated inTable 2 and spun into fibers having a titer of approx. 1.2 to approx.1.6 dtex by a spinning method according to WO 93/19230 under theconditions of Table 2.

Constant parameters not indicated in the table are:

the spinning mass output of 0.02 g/hole/min

the air gap of 20 mm

the humidity of the blowing air of 8-12 g H₂O/kg air

the temperature of the blowing air of 28-32° C.

the speed of the blowing air in the air gap of 2 m/sec

The textile-mechanical data of the obtained fibers are indicated inTable 3. The Höller factors calculated from the textile data, the wetabrasion value and the flexibility of the fibers can be seen in Table 4.The results clearly show the impact of the pulp and the particularimportance of the spinning temperature.

TABLE 1 limiting amount viscosity alpha of DP < number content 50 DP >Pulp code ml/g % % 2000 Solucell 250 So 250 270 91.8 1.3 2.8 BorregardDerivative Bo HV 1030 n.b. 1.4 49.1 HV Saiccor Sai 383 90.4 6.6 14.9Borregard Derivative Bo VHV 1500 92.7 n.b. n.b. VHV Solucell 400 So 400415 94.9 1.9 11.8 Cotton Linters low Co LV 396 97.1 0.6 0 MW CottonLinters high Co HV 2030 99.1 0 98.3 MW Reclaimed cotton RCF LV 423 97.10.45 7.7 fibers, low MW Reclaimed cotton RCF HV 1840 97.8 0 68.7 fibers,high MW

The pulps “RCV LV” and “RCV HV” were produced according to the teachingof the publication “Process for pretreating reclaimed cotton fibers tobe used in the production of moulded bodies from regenerated cellulose”(Research Disclosure, www.researchdisclosure.com, database number609040, published digitally Dec. 11, 2014).

TABLE 2 cellulose water pulp or pulp ratio high-molecular in spinning inspinning spinning spinning bath mixture, amount/low- mass mass nozzletemperature temperature respectively molecular amount % % μ draft ° C. °C. Example 1 Co HV/Co LV 10/90 11 12 40 1.54 131 0 Example 2 Co HV/Co LV10/90 11 12 50 2.41 131 0 Example 3 Co HV/Co LV 10/90 11 12 60 3.47 1300 Example 4 Co HV/Co LV 10/90 11 12 80 6.17 130 0 Example 5 Co HV/Co LV10/90 11 12 60 3.47 130 20 Example 6 Co HV/Co LV 10/90 11 10.5 50 2.41132 0 Example 7 Co HV/Co LV 10/90 11 10.5 50 2.41 132 20 Example 8 CoHV/Co LV 10/90 13 11.7 50 2.85 131 0 Example 9 Co HV/Co LV  5/95 13.5 1050 2.96 130 20 Example 10 Co HV/Co LV  5/95 13.5 10 50 2.96 131 0Example 11 Bo HV/So 250 30/70 11 12 40 1.54 130 20 Example 12 Bo HV/So250 30/70 11 12 50 2.41 130 20 Example 13 Bo HV/So 250 30/70 11 12 603.47 130 20 Example 14 Bo HV/So 250 30/70 11 12 70 4.73 130 20 Example15 Bo VHV/So 400 24/76 11 12 50 2.41 132 20 Example 16 RCF HV/ 10/90 1112 50 2.41 130 0 RCF LV Example 17 Bo VHV/ 10/90 11 12 50 2.41 132 0 RCFLV Comparative Co HV/Co LV  5/95 13.5 10 50 2.96 122 0 Example 1Comparative Co HV/Co LV 10/90 11 12 100 9.64 130 20 Example 2Comparative Sai 12.8 10.5 40 1.80 132 20 Example 3 Comparative Sai 1310.5 100 11.4 124 20 Example 4 (commercial Lyocell fiber)

TABLE 3 titer FFk FDk FFn FDn NM SFk KFk dtex cN/tex % cN/tex % cN/tex,5% cN/tex cN/tex Example 1 1.37 21.8 15.2 16.7 22.8 4.2 14.8 21.3Example 2 1.37 25.1 21.5 17.8 28.2 3.9 15.7 23.3 Example 3 1.37 26.417.4 19.0 22.2 4.8 16.3 23.3 Example 4 1.37 26.3 16.5 20.8 22.8 5.4 17.525.1 Example 5 1.36 26.0 14.0 17.5 20.5 4.7 14.5 22.7 Example 6 1.2324.5 19.0 18.7 25.5 4.4 16.1 22.5 Example 7 1.34 24.7 17.5 20.0 24.4 5.516.7 24.1 Example 8 1.54 26.4 16.1 19.5 21.7 4.7 17.4 23.6 Example 91.29 27.5 14.9 20.5 21.0 5.8 20.6 24.9 Example 10 1.37 24.8 17.8 19.424.2 4.5 19.1 23.6 Example 11 1.34 21.3 14.1 14.9 22.8 3.6 11.5 19.2Example 12 1.30 24.1 15.2 15.4 19.2 4.4 10.2 19.4 Example 13 1.37 22.915.9 18.1 22.7 4.4 11.1 20.3 Example 14 1.30 25.3 14.6 19.4 21.8 5.012.0 20.5 Example 15 1.30 27.5 16.9 22.7 22.8 6.0 13.2 23.8 Example 161.36 24.6 16.0 18.5 23.9 4.2 14.8 22.4 Example 17 1.32 23.1 16.5 17.924.5 4.0 14.1 20.9 Comparative 1.30 28.8 15.0 21.1 23.6 5.3 20.9 25.2Example 1 Comparative 1.43 27.7 11.1 21.6 16.1 8.1 16.7 25.0 Example 2Comparative 1.31 30.1 13.5 22.3 16.4 6.9 11.3 21.1 Example 3 Comparative1.37 39.3 13.6 34.9 18.6 10.6 18.9 31.7 Example 4 commercial Lyocellfiber

TABLE 4 Höller wet abrasion value factor Höller factor revolutions untilflexibility F 1 F 2 breakage FDk/FFk Example 1 −0.05 3.20 1951 0.70Example 2 −0.45 4.39 1947 0.86 Example 3 0.27 4.22 664 0.66 Example 40.51 4.88 370 0.63 Example 5 0.40 3.33 244 0.54 Example 6 −0.12 4.161427 0.78 Example 7 −0.07 5.02 1455 0.71 Example 8 0.42 4.53 511 0.61Example 9 0.84 5.61 303 0.54 Example 10 0.17 5.15 635 0.72 Example 11−0.28 1.82 336 0.66 Example 12 −0.04 1.45 585 0.63 Example 13 −0.09 2.06410 0.70 Example 14 0.27 2.36 312 0.58 Example 15 0.52 3.49 443 0.62Example 16 0.08 3.59 1153 0.65 Example 17 −0.14 3.13 821 0.71Comparative 1.21 5.94 332 0.52 Example 1 Comparative 1.45 4.16 125 0.40Example 2 Comparative 1.05 2.17 30 0.45 Example 3 Comparative 2.72 6.1740 0.34 Example 4 commercial Lyocell fiber

FIG. 3 shows the position of the examples/comparative examples in theHöller chart as well as the area of the chart which is claimed accordingto the invention. Therein, examples 1 to 17 (according to the invention)are designated with their respective numbers, while the comparativeexamples 1 to 4 are designated with a pre-fix “V”, respectively.

Comparative Example 1 demonstrates that the object according to theinvention is not achieved if the spinning temperature, which, at 122°C., is below the required value of at least 130° C. even if allremaining manufacturing parameters correspond to the parameters for theproduction of the fiber according to the invention.

Comparative Example 2 demonstrates that the object according to theinvention is not achieved if the draft, which, at 9.64, is above therequired value of less than 8.00, even if all remaining manufacturingparameters correspond to the parameters for the production of the fiberaccording to the invention.

Comparative Example 3 demonstrates the significance of the pulp. Theobject according to the invention is not achieved if the pulpcomposition, which, with a single pulp, fails to exhibit the necessaryproportion of a very high and a low molecular weight, even if allremaining manufacturing parameters correspond to the parameters for theproduction of the fiber according to the invention.

Comparative Example 4 shows the properties and the position in theHöller chart of a commercial Lyocell fiber (Tencel® of Lenzing AG).

Processing Example

A 130 kg bale of a fiber of 1.3 dtex/38 mm according to Example 11 wasprocessed into a ring yarn Nm 50. A single jersey with a mass per unitarea of 150 g/m2 was produced from said yarn. A sample of this singlejersey was dyed with 4% Novacronmarine FG, bath ratio 1:30, at 60° C. ina laboratory jet for 45 min and subsequently subjected to 15 householdwashings at 60° C.

Table 5 shows the abrasion and washing behavior of this single jersey incomparison to a planar assembly of the same structure made of acommercial viscose or Lyocell fiber, respectively.

TABLE 5 Lyocell Fiber according to viscose 1.3 standard 1.3 Example 11dtex dtex Abrasion Martindale 57 500 58 750    15 500    tours untilhole formation Washing test Grey scale* Grade after 1st washing 4-5 43-4 Grade after 5th washing 4-5 4 1 Grade after 10th washing    3 4-5 2Grade after 15th washing 2-3 4-5 1 *Grades from 1 to 5, the best gradeis 5

1) A cellulosic fiber of the Lyocell type which has a titer of from 0.8dtex to 3.3 dtex and is characterized by the following relationships:Höller factor F2≥1, preferably ≥2 Höller factor F1≥−0.6 Höller factorF2≤6 and Höller factor F2 minus 4.5*Höller factor F1≥1, preferably ≥3.2) The fiber according to claim 1, characterized by a wet abrasionresistance amounting to between 300 and 5000 revolutions. 3) The fiberaccording to claim 1 or 2, characterized by a flexibility of between0.55 and 1.00. 4) The fiber according to any of the preceding claims,wherein a single jersey 150 g/m2 produced from a ring yarn Nm 50/1 ofsaid fiber exhibits an abrasion resistance according to Martindale ofbetween 30 000 and 60 000 tours up to the point of hole formation. 5)The fiber according to any of the preceding claims, characterized inthat it is produced according to the amine oxide process. 6) The fiberaccording to any of the preceding claims, characterized in that it isproduced from a mixture of at least two different pulps. 7) A fiberbundle comprising a plurality of fibers according to any of thepreceding claims.